General News

Dr. Aaron Breneman, researcher in the School of Physics and Astronomy, was lead author on a paper which helps explain the mechanism which causes highly energetic electrons that reach the Earth’s atmosphere. Such particles can cause the auroral displays--the Northern Lights in Northern Minnesota, for example, and can damage satellites and other spacecraft. One of the goals of this research is to help predict space “weather” which can adversely affect human activity and technology.

Using data from NASA’s Van Allen Probes mission and Firebird II, Breneman and his colleagues pinpointed short bursts of whistler waves, a wave which makes a sound like chirping birds, just prior to a burst of energetic particles. Professor John Wygant is the PI on the Electric FIelds and Waves instrument on the Van Allen Probes. FIrebird II is a small satellite the size of a shoebox, called a CubeSat, built by students at the University of New Hampshire and Montana State University.

The Earth’s magnetic field traps relativistic electrons and protons in a large invisible ring around the planet. These rings, called the Van Allen Radiation belts, usually keep the particles trapped, with only a only a few slowly leaking out. Occasionally, highly energized electrons escape and collide with the Earth’s upper atmosphere neart the poles. These fast moving electrons are called microbursts and last for just fractions of a second.

On January 20, 2016, the Van Allen Probes observed whistler waves from its position within the Van Allen belts and immediately after, FIREBIRD II detected microbursts. “Observing the detailed chain of events between chorus waves and electrons requires a conjunction between two or more satellites,” said Breneman. “There are certain things you can’t learn by having only one satellite — you need simultaneous observations at different locations.”

The paper confirms that the whistler or “whistler mode chorus waves” play an important role in the behavior of microbursts, bringing them a step closer to understanding the phenomenon.. And now that physicists have confirmed that whistler waves immediately precede a microburst, this information can be used to improve space weather predictions.